This invention relates generally to devices for separating dissolved or entrained gas from a liquid, and, more particularly, to devices for the separation of air from a working fluid used in hydraulic systems or from fluids used as insulators in electrical systems.
The working fluid in hydraulic systems, for example, typically absorbs or dissolves air readily through pressure seals and pumps suction lines, as well as during system flushing and filling. Air introduced by any means into such a system is dissolved or entrained in the oil, or it may find its way to various corners or "quiet spots" in the system. Clearly, any significant accumulation of air in a hydraulic system adversely affects various physical properties of the oil, and can result in sudden and often disastrous failure of hydraulically operated components. Such a problem in hydraulic systems is aggravated in aircraft applications by low pressures encountered in high altitude flight which cause any dissolved air to be released into the system from the hydraulic fluid.
Various devices have been developed to "degas" hydraulic or electrical insulation systems, many using a vacuum pump connected to a container of the fluid. Use of vacuum pumps is generally unsatisfactory for a number of reasons. For example, the fluid undergoing degassing tends to froth and to be drawn into the pump. Also, there are often substantial maintenance problems with vacuum pumps.
A significant advance in degassing devices occurred with the development of the "Gas-Oil Separator" which is the subject of U.S. Pat. No. 3,358,424 issued to Vincent G. Magorien and assigned to the same assignee as the present invention. The Magorien device includes no vacuum pumps and employs a cyclic degassing technique which overcomes many of the disadvantages of its predecessors. However, it was intended primarily for degassing aircraft hydraulic and other systems on the ground, and certain of its features make it unsuitable for use in airborne or industrial environments. For example, a large float is used to actuate a cycling valve in the device, but the buoyancy and weight forces of the float may be insufficient to operate the valve consistently when the device is subject to particle contamination, variations in oil viscosity, or changes in aircraft attitude.
There has long existed, therefore, a need for a fluid degassing device, without vacuum pumps and other hard-to-maintain components, which can operate continuously in an airborne or industrial environment which is subject to contaminating solid particles, variations in temperature and pressure, and rapid changes in attitude, including possible temporary inversion. A need also exists for an airborne degassing device which can remove relatively large quantities of trapped air from specific pockets in a hydraulic system, as well as smaller, entrained and dissolved amounts. For example, sealed reservoirs, called "bootstrap" reservoirs, are commonly used in modern aircraft for improved pressurization and inverted flight. However, they are susceptible to air entrapment, and an airborne degassing device should also provide for the removal of such large quantities of entrapped air. The present invention satisfies the foregoing requirements.